The process of muscle contraction


Arrival of an action potential:

  • When an action potential from a motor neurone stimulates a muscle cell, it depolarises the sarcolemma. 
  • Depolarisation spreads down the T-tubules to the sarcoplasmic reticulum. This causes the sarcoplasmic reticulum to release stored calcium ions into the sarcoplasm. This influx of calcium ions into the sarcoplasm triggers muscle contraction.
  • Calcium ions bind to a protein attached to tropomyosin, causing the protein to change shape. This pulls the attached tropomyosin out of the actin-myosin binding site on the actin filament.
  • This exposes the binding site, which allows the myosin head to bind. 
  • The bond formed when a myosin head binds to an actin filament is called an actin-myosin bridge.

Movement of the actin filament:

  • Calcium ions also activate the enzyme ATP hydrolase which hydrolyses…


No comments have yet been made